Handheld meter robustness testing

[joeqsmith]

Sorry you Keysight fanboys.   I am unable to continue the 50,000 cycle life test.   I left a clue in the photo for you.   

Considering I even put that last UNI-T meter through this same test, seeing two Keysight meters do so poorly with this test is just one more disappointment to add to the list.   It's not a free meter from Harbor Freight. 

[Fungus]

I did write Dave about the U1282A that he swam with, drove over, tossed off the bridge, threw against the wall to see if he would be willing to part with the PCB to possibly salvage this meter.  Maybe we will get lucky.

Doesn't seem much point any more...

[GuidoK]

Sorry you Keysight fanboys.   I am unable to continue the 50,000 cycle life test.   I left a clue in the photo for you.   

But you are making a video about it...right? 

BTW, I was wondering about the grill starter test.
In the video's it's not very visible, but I think you hold the end of the grill starter physically to the multimeter input terminal, right?
Does it make a difference when you don't do that and let it hoover slightly above that input terminal (say 1mm or so) and when you press the button, there is a spark over that airgap?
Won't that ramp up the voltage considerably? (because of the extra resistance of the air gap)
Or is the total path of resistance then so high (airgap plus resistance in the meter itself) that no spark is even happening?

[joeqsmith]

But you are making a video about it...right? 

Yes 

BTW, I was wondering about the grill starter test.
In the video's it's not very visible, but I think you hold the end of the grill starter physically to the multimeter input terminal, right?

Both ESD transients are direct contact.

Does it make a difference when you don't do that and let it hoover slightly above that input terminal (say 1mm or so) and when you press the button, there is a spark over that airgap?

Yes

Won't that ramp up the voltage considerably? (because of the extra resistance of the air gap)
Or is the total path of resistance then so high (airgap plus resistance in the meter itself) that no spark is even happening?

Maybe watch the following starting about 8:30.   
***
Note that this probe (and scope) would not have the bandwidth to actually look at these transients.  All I am doing in this video is trying to get some idea where the probe will breakdown.  When I looked at the grill starter with my homemade target, I used my old 5GHz LeCroy. 

[joeqsmith]

Towards the very end of this video, I show an old spark plug that uses two different gaps.  One adjustable, one fixed that ignites the mixture.   The adjustable one also can be closed up.   As we increase this secondary gap, we increase where it will breakdown and increase the current through the second gap.  In my youth, I would do this manually by lifting the boot to clear out a fowled plug on my 2-stroke bikes.

[joeqsmith]

Dog4 watching while I drag out scopezilla to have a look at whats left of the Keysight meter.    Plan to wrap things up today. 

Dog4 has been with us almost 2 years now after the original owner had abandoned her at a kill shelter.  She gets a lot of exorcise and her overall health has improved.    Her eyesight was starting to fail and we discovered she has Pannus which is an autoimmune disease.   It's nothing I have ever heard of and to me, it looks like a cataract. 
Its more common in certain breads like German Shepherds.  If caught early enough the effect can be reversed.   Left untreated.....   She will have eye drops the remainder of her life and it is clearing up.   Something to be aware of.

[Fungus]

Dog4 has been with us almost 2 years now.  She gets a lot of exorcise

Demonic dog? You need to be very careful with those...

[joeqsmith]

exercise     Still, she does have a bit of an evil streak about her.  Likes to take things from the lab while I am looking right at her.  Doesn't shew them but takes off running.  Then it's off for some play time.   

[joeqsmith]

Conclusion

[Fungus]

Thanks for showing the stepper motor setup in detail.

Do you adjust the maximum motor torque for each test based on the force required to turn the dial?

[joeqsmith]

Thanks for showing the stepper motor setup in detail.

Do you adjust the maximum motor torque for each test based on the force required to turn the dial?

Wait, nothing about rubust and shews??      

Yes.  If you watch the following video, starting around 6min in or so, I go over the cycle test in more detail.   When you watch the Keysight U1282A, note that when the software initially tries to move the motor, the current is already too low and it stalls right away.  The Keysight meter has a lot more drag than the Brymen shown.  When I set the starting current where I start to look for the stall, this is the first time it was not high enough to get the switch to rotate.   The motor can produce more torque but nothing like I can with my hand..   

You may remember my posting about loaning out a meter and the person turning the knob past the dead stop and breaking the plastic.   That was a cheap CEM.  I could see something similar happening to this meter once the drag gets so high.  I suspect many users will try to force it.  If that doesn't work, the hammer is next.   

Good job Keysight!!
Over spec the frequency input  (Defpom claims they are changing the paper work to address this)
Data logging that glitches
Lettering that comes off easily
Poor input protection that not only allows damage to the meter at fairly low voltages, but does not protect the sensitive ICs that can not be replaced (can you say disposable)
A function switch that can't survive even a fifth of what the better class of meters can handle

I guess it's water tight so if you want to go swimming with it, you're good to go!   

[gnavigator1007]

Good job Keysight!!
Over spec the frequency input  (Defpom claims they are changing the paper work to address this)
Data logging that glitches
Lettering that comes off easily
Poor input protection that not only will damage the meter at fairly low voltages, but does not protect the sensitive ICs that can not be replaced
A function switch that can't survive even a fifth of what the better class of meters can handle

It even says right on the box:
Retool Your Expectations

 

[joeqsmith]

 

[Fungus]

Will we see the new 2000V Uni-T be subjected to the grill starter?

[GuidoK]

I was wondering:
Have you ever cycle tested the rotary switch on one of the smaller Brymen meters?
I couldn't find anything about that.
I believe you have the BM235 and BM319 that fall in that form factor?
I saw both the BM869S and BM839 cycle tested, and results were similar after 50k cycles, and I guess that makes sense as they're situated in virtually the same housing and the switch also looks virtually the same.
But the BM235 and BM319 have a smaller housing and maybe a differently sized switch? It would be interesting to see how those smaller meters performed in the switch cycle test.

[joeqsmith]

I was wondering:
Have you ever cycle tested the rotary switch on one of the smaller Brymen meters? I couldn't find anything about that.

Assuming physical size,  I ran a BM786 which is physically much smaller than the BM869s.     

I believe you have the BM235 and BM319 that fall in that form factor?
I saw both the BM869S and BM839 cycle tested, and results were similar after 50k cycles, and I guess that makes sense as they're situated in virtually the same housing and the switch also looks virtually the same.
But the BM235 and BM319 have a smaller housing and maybe a differently sized switch? It would be interesting to see how those smaller meters performed in the switch cycle test.

I have not ran Dave's rebranded BM235 I bought from him.   We do know that Brymen does run a similar test on their products.   I've posted a few clips of their setup.   I think they actually had a similar meter on their jig in those clips.   

[GuidoK]

I've posted a few clips of their setup.   I think they actually had a similar meter on their jig in those clips.

Ok, but having a meter on their jig is not the same as showing the result of the test of course. BTW if I look at those clips from Brymen, to me it looks like a BM869s and some current clamp is shown, but the clips are not very clear and maybe I'm looking at the wrong clips. (I look at the clips you show in your BM869s life cycle video; funny enough the rotary switch from what I believe is a BM869s in the Brymen video doesn't sound very healty to me (the clicking), but in your test the indent spring had no wear whatsoever; but of course we don't know what was in that Brymen meter in the video from Brymen, they just as well might have been experimenting with glass fibre reinforced plastics for indent springs  )

Looking at your video's, it looks like the switch of the small form factor meters like the BM235 and BM319 have quite a different construction to the BM869s or BM786, where the BM235/319 have the swipe contacts integrated in the part with the indent spring (which also looks to be somewhat different) and mated on the front housing part instead of a seperate construction piece that is screwed to the pcb.
I can't make a good size or construction comparison myself between the small and larger brymen meter rotary switches, I look at your video's for that. I only have a BM869s, and don't own a BM235 or other meter in that small form factor.

The BM869s and BM786 look somewhat similar, but it looks the BM869s seems to have switch contacts on both sides and the BM786 not, but on both of those meters the swipe contacts are housed in a separate construction that is screwed to the pcb.

So I think a life cycle test on the BM235/319 rotary switch would still give interesting information due to the different construction. At least interesting for people that own a Brymen in that small form factor or plan to buy one.

[joeqsmith]

I wonder if Dave ever ran the BM235.

[joeqsmith]

I've shown my ESD targets (low inductance current shunts) and how I mounted the SMD resistors inside the two layers of PCB.   Here is a video explaining in more detail how to make some simple shunts. 

[joeqsmith]

I've had a lot of people asking me about my transient generator.   Here you can see one of the forum members attempting to construct their own combo generator that follows the IEC standard.   The claim is they can reproduce the open circuit voltage and short circuit current waveforms with their prototype, which they show.   It may be of interest to a few of you.   

https://www.eevblog.com/forum/beginners/what-are-the-tricks-for-winding-a-tight-air-core-inductor/msg4356235/#msg4356235

[GuidoK]

I was looking at some of your old video's, particularly about the Fluke 17B+, and I noticed a perculiar thing.
In the first review/testing of the Fluke 17B+, you made a remark about that the switch was so lubed up.
It also can be shown in this video @ 4:48:
https://youtu.be/wiiii0gdcbM?t=288
You also commented about this in this post:
https://www.eevblog.com/forum/testgear/hear-kitty-kitty-kitty-nope-not-that-kind-of-cat/msg809665/#msg809665

But when life cycle testing the rotary switch from the 17B+, you state that the switch contacts are dry.
In this video (about the life cycle testing) at 21:22 you show that it's the meter you repaired, showing parts that you've resoldered, but the switch of that meter is completely dry (as seen a moment later in the same video (at 22:15):
https://youtu.be/x_L6Z8BAXFQ?t=1282

So my question is: what happened here? Is this the same meter that you used in the first test? And are Fluke 17B+ rotary switch contacts lubed or not?
I don't really understand what happened here, but it doesn't seem logical to me.
I searched in this thread but couldn't find a real explanation for this.

[joeqsmith]

So my question is: what happened here? Is this the same meter that you used in the first test? And are Fluke 17B+ rotary switch contacts lubed or not?
I don't really understand what happened here, but it doesn't seem logical to me.
I searched in this thread but couldn't find a real explanation for this.

It seems perfectly logical to me.   What happened?  I would say "time" happened.   From the first video dated Dec 2015, it was supplied with lubrication.   In that same video the meter had been damaged and I talk about ordering parts to repair it.   It doesn't appear I made a follow up video showing the repairs.  There's no magic disappearing grease.  I obviously cleaned the PCB when working on it.   

I'm guessing I had no plans to do anything more with the meter (as far as transient testing it again) and never reapplied grease to the contacts.  That or by the time the parts arrived, I had already cleaned the board when removing the part and just forgot to replace it.    Fast forward two years to Nov 2017,  when I started to look at life cycling switches and pulled this meter out of the box as fodder.   The contacts were still dry. 

Now of course, there may be some question on how the grease would have effected the life cycle test.  Oldly enough, this meter remains one of the best switches I have looked at running with dry contacts.  The 17B+ was damaged at a fairly low level compared with other Fluke products I looked at and I wonder if the leaving the grease off would have caused it to fail at an even lower level.   Hard to say.

Mystery solved.   Old hobbyist reviewing meters.    Great question BTW.  Good to see someone paying attention! 

[Grandchuck]

How about that!

[arcitech]

I think this could require big changes to a meter's front-end, but I'd love to see if the FLIR DM92/3 would "come-a-gutza" under your hands! At this level it competes with Fluke, so if we could get Flir to send you one, it would be nice to know if the switch can take a good beating too. I bet you'd knock it out with the grill starter and send them back to the drawing board 

For what it's worth, a US-based T&M shop has DM92 meters available at $179+shipping on eBay, and (not that it matters to Joe I'd suppose) has confirmed that their shop is an authorized FLIR distributor. It's a far cry from their (own) website's listing at $299. Maybe for this price, it's worth a shakedown..?

(I've avoided links and name of the shop in hopes of not jeopardizing authorized distributor standing; I certainly don't claim to know the rules, but would imagine those who do are likely under NDA, so I'll assume putting names/links on blast would be somewhat irresponsible.)

[paulbt]

Hello!

I searched on this forum for "multimeter input protection", but I could not find anything related other than this topic.

I have a crappy Axiomet dmm with no input protection. I wanted to have some fun with it so I cut some traces and added in series with V/ohm input a 2W 1K resistor, a 1K PTC and a MOV back to COM input.

After this, voltage measurement is 'good' as before, but resistance measurement is affected by the added components. No surprise for me, when I short the leads I get ~2K reading.

I watched again Dave's video on this, but I could not understand how they manage to read the resistance correctly and to have overload protection at the same time.

Can anyone please explain it for me?

If you know any discussion about this on the forum, please post a link here.

Also, please see the attached pictures.